Which wars are just or unjust?

Civil War: the disagreements within our own country needed to be resolved

War On Terror: 9/11 caused us to go to war

Gulf War: we needed to protect our shores

World War I: assisting Europe

Unjust

War of 1812: it wasn't necessary because we didn't need to take over the other countries

Mexican American War: wanted Texas

Red Rivers War: arguement over the rivers for the Natives

Vietnam War: the only reason we fought to attempt to solve communism

Korean War: it was not necessary to get involved

World War I

1914-1918

World War I started when Austria declared war on Serbia. It was supposed to be a very small war but it ended up involving multiple others because various European countries has treaties to protect each other. It was more of an obligation. During this war they used trench warfare and machine guns to defend themselves. Britain, at the time was the top country. Germany wanted to take control but was not able to because they were too weak. Germany sent a letter to Mexico telling them to join saying that they could work together to destroy the US, but Mexico didn't want too. The US eventually found out, therefore going to war.